The auditory cortex exhibits a broad range of response modes spanning from phasic, single spike or binary[unreadable] responses to tonic, multi-spike, sustained random firing sequences per stimulus. The goal of this project is to[unreadable] determine the character of response variability of different types of auditory cortical neurons in the awaken[unreadable] squirrel monkey. This will allow us to assess the potential role and influence of variability on neuronal[unreadable] encoding, and its impact on behavioral performance and to compare the results to other response[unreadable] modalities. To achieve this, it is necessary to obtain simultaneous estimates of neural and behavioral[unreadable] performance in the awaken animal. Response variability will be assessed under three conditions, in the[unreadable] passive listening animal to serve as a baseline, in the animal actively involved in a behavioral sound[unreadable] discrimination task to assess attention effects, and in animals that are highly trained to assess the effects of[unreadable] learning on the expression of response variability. In conjunction with the other projects, these studies will[unreadable] contribute to establishing general rules, across sensory and motor systems, of the nature and role of[unreadable] response variability in the generation of behavior.